Fibrinogen (Fg) and fibrin (Fb) are hydrolyzed by the blood enzyme, plasmin, in pathological fibrinogenolysis and fibrinolysis. Plasma concentrations of Fg and/or Fb degradation products (FDP) are thus augmented. Since abnormal quantities in plasma indicate that the hemostatic equilibrium is disturbed, a rapid and accurate measure of FDP would be clinically valuable. The problem will be approached by: (1) Production simply and efficiently of neoantigenic antisera against FDP; (2) Development of radioimmunoassays for fibrinogen/fibrin degradation products in plasma. Attempts will be made to produce antibodies specific only to the E fragment of fibrin by using the principle of immunological tolerance in order to produce antibodies capable of detecting "hypercoagulable states". Radioimmunoassays capable of discriminating between FbDP and FgDP in human plasma will be developed. Hyper- and hypocoagulable states will be evaluated through immunoassays of FDP which will distinguish between a primary fibrinolytic state and a disseminated intravascular coagulation followed by secondary fibrinolysis.